Liquid measuring device

ABSTRACT

A liquid measuring device is described for carrying out the assay using a gas or vapor permeable but liquid impermeable membrane barrier to control the volume of liquid to be measured or transferred. The membrane may be used in any instance where a fixed volume of liquid needs to be measured.

RELATED APPLICATIONS

This application is a continuation of U.S. Ser. No. 10/042,906, filedJan. 9, 2002 and a continuation of U.S. Ser. No. 10/042,904, filed Jan.9, 2002 which are both continuations of U.S. Ser. No. 09/810,875, filedMar. 16, 2001, now U.S. Pat. No. 6,360,595, issued Mar. 26, 2002.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The field of the invention relates to an apparatus and a method forusing the apparatus for the measurement and/or transfer of a fixedvolume of liquid sample.

2. Description of the Related Art

General methods to determine o-phthalaldehyde (OPA) or glutaraldehydeconcentrations are mainly instrumental measurements that could beclassified into chromatographic measurement (chromatographic, HPLCanalysis) or non-chromatographic measurement (direct spectroscopicassay). For HPLC analysis, OPA or glutaraldehyde are measured by both aderivative method or a non-derivative method. The most common derivativemethod is to convert OPA or glutaraldehyde to2,4-dinotrophenylhydrazones by reacting OPA with2,4-dinitrophenylhydrazine. Since the UV absorption is greatly enhanced,this method is valuable for low level OPA or glutaraldehyde measurementsespecially in environmental analysis. For measurements of highconcentrations of OPA or glutaraldehyde, such as the OPA orglutaraldehyde disinfectants, OPA or glutaraldehyde could be measureddirectly without making derivatives first. OPA or glutaraldehyde may beanalyzed easily with GC analysis. For non-chromatographic analysis, OPAor glutaraldehyde could be measured directly with spectrophotometricmethods. However, one drawback to this method is that there must be nointerference at the specific wavelength used. For example, OPA orglutaraldehyde could be oxidized slowly by air and the carboxylic acidformed may interfere in such assays.

All three instrumental methods involve the preparation of samples anduse of an instrument. They are all time-consuming and too expensive ortoo complicated for hospital end users. Therefore, Albert Browne and 3Mhave developed a simple strip procedure for a Pass/Fail test. In such atest, the strip was dipped into either OPA or glutaraldehyde solutionsfor a certain amount of time. After a predetermined time, the stripcolor was compared with some standard colors. Their strip chemistryprinciples were not released. The problems with this method areconsistency and accuracy. The strip method has the following problems(1). Good solutions (OPA or glutaraldehyde higher than “POI”, the pointof interest) often fail the test for different reasons. (2). The soakingtime and waiting time have to be controlled carefully. Any deviationwill lead to different shades of color and a false reading. (3). Movingof the strip when soaking will lead to the loss of chemical reagents tothe OPA or glutaraldehyde solutions leading to false reading. (4).Individual users have different color recognition habits and often havea different opinion of the end-color. (5). The final color is dependenton many factors and is particularly sensitive to time.

The current invention provides another method without the aboveproblems. Although the chemistry principle could also be used for thestrip approach, in a preferred embodiment it is used for the colorchange of a solution.

SUMMARY OF THE INVENTION

The present invention pertain to a liquid measuring device that measuresa fixed volume of liquid including a first barrel having a proximal anddistal end and a gas or vapor permeable but liquid impermeable barriersituated in the barrel between the proximal and distal ends, whereby theliquid can only be filled up to the barrier. In a preferred embodiment,the volume in the barrel up to the barrier equals the fixed volume. Theliquid measuring may further include a means to position the barrier todeliver a fixed volume of liquid, whereby the liquid can only be filledup to the barrier.

In a preferred embodiment, the liquid measuring device further includesa coupling device to adapt the barrier to the measuring device. In amore preferred embodiment, the coupling device includes an insert. In amost preferred embodiment, the insert is movable in the barrel. Inanother most preferred embodiment, the liquid measuring device furtherincludes a holder to position and secure the insert in the liquidmeasuring device. In an alternate preferred embodiment, the insert ismoved to a desired position by means of a screw.

In a preferred embodiment, the liquid measuring device is a pipette orsyringe.

In a preferred embodiment, the liquid measuring device further includesa second barrel which is in fluid communication with said first barrelby means of a valve. In a preferred embodiment, the valve is a one-wayvalve. In an alternate preferred embodiment, the valve has an on/offswitch.

In a preferred embodiment, the liquid measuring device may furtherinclude a needle at the distal end.

In a preferred embodiment, the insert of the liquid measuring device isH-shaped in cross-sectional view. In an alternate preferred embodiment,the insert is U-shaped in cross-sectional view.

In a preferred embodiment, the first barrel of the liquid measuringdevice includes a valve at the distal end. In a more preferredembodiment, the valve is a one-way valve. In an alternate more preferredembodiment, the valve is an on/off valve. In a preferred embodiment, thegas or vapor permeable but liquid impermeable barrier of the liquidmeasuring device comprises hydrophobic material.

The present disclosure also pertains to a method of measuring a fixedvolume of liquid including the steps of:

1) providing a gas or vapor permeable but liquid impermeable barrier ina barrel having a proximal end and a distal end;

2) inserting the distal end into a sample comprising liquid fluid;

3) creating a negative pressure on the proximal end; and

4) transferring the liquid fluid from the sample into the barrel,wherein the liquid fluid can only be filled up to the barrier.

In a preferred embodiment, the method further includes adjusting theposition of the barrier in the barrel. In a preferred embodiment, thebarrier is part of a coupling device and the method further includesadapting the coupling device to the barrel. In a more preferredembodiment, the adapting includes inserting the coupling device into thebarrel.

In a preferred embodiment, the barrel further includes a valve at thedistal end and the method further includes opening and/or closing thevalve.

In a preferred embodiment, the method further includes pulling a plungerin the barrier to create a negative pressure.

For purposes of summarizing the invention and the advantages achievedover the prior art, certain objects and advantages of the invention havebeen described above. Of course, it is to be understood that notnecessarily all such objects or advantages may be achieved in accordancewith any particular embodiment of the invention. Thus, for example,those skilled in the art will recognize that the invention may beembodied or carried out in a manner that achieves or optimizes oneadvantage or group of advantages as taught herein without necessarilyachieving other objects or advantages as may be taught or suggestedherein.

Further aspects, features and advantages of this invention will becomeapparent from the detailed description of the preferred embodimentswhich follow.

BRIEF DESCRIPTION OF THE DRAWINGS

These and other feature of this invention will now be described withreference to the drawings of preferred embodiments which are intended toillustrate and not to limit the invention.

FIG. 1 shows the basic principles of the described assay. Reaction 1shows the reaction of aldehyde with compound X to produce a compoundwith a first color. Preferably, the first color is colorless. Reaction 2shows the reaction of aldehyde and Y to form a compound with a secondcolor. Preferably, reaction 2 is slower than Reaction 1. If theconcentration of aldehyde is below the POI (point of interest) onlycompound X will react and the resulting solution will be the first coloras shown in the bottom half of the figure. In the presence of a level ofaldehyde that is equal to or more than the POI, a solution with thesecond color or the combined color of the first color and the secondcolor will be formed.

FIG. 2 shows a pipette and two variants of a syringe with a gas or vaporpermeable liquid impermeable barrier.

FIG. 3A shows the coupling of the gas or vapor permeable liquidimpermeable barrier to the syringe or pipette. FIG. 3B illustrates howinserts 4 at the top of the pipette or syringe attach the gas or vaporpermeable liquid impermeable barrier to the pipette or syringe. FIG. 3Cillustrates a holder 5 that holds the inserts in place. FIG. 3D showsthe inserts and the coupling of the gas or vapor permeable liquidimpermeable barrier.

FIG. 4 is an expanded view of FIG. 3C which shows a gas or vaporpermeable liquid impermeable barrier 1, an insert 4, and a holder 5.

FIG. 5 shows one embodiment of the invention where the position of thegas or vapor permeable liquid impermeable membrane is adjusted by meansof a screw.

FIGS. 6A and 6B show embodiments of the liquid delivery apparatus withall chemicals in one chamber. FIG. 6C shows a two chambered embodimentof the liquid delivery apparatus. The test sample may be taken into thefirst chamber for reaction with the first compound such as compound X inFIG. 1. Then the sample is moved by means of a one-way valve or a manualON/OFF valve 8 into the second chamber where the test sample reacts withthe second compound such as compound Y of FIG. 1.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

While the described embodiment represents the preferred embodiment ofthe present invention, it is to be understood that modifications willoccur to those skilled in the art without departing from the spirit ofthe invention. The scope of the invention is therefore to be determinedsolely by the appended claims.

Aldehydes react with amino-containing compounds like amino acids oramines to form an imine or more commonly known as a Schiff's base, whichis often colored. Taking glycine as an example:

Another known aldehyde reaction is the sodium bisulfite carbonyladdition reaction.

The sodium bisulfite addition reaction is more favorable than that ofSchiff's formation since the former reaction is fast and hard toreverse. Thus, in the presence of both a compound containing an aminogroup such as an amino acid and a reagent such as sodium bisulfite, thealdehyde will react first with sodium bisulfite and then with the aminoacid. Therefore, it is possible to design a color pass/fail reaction bycontrolling the amount of reagents to react with aldehydes such asformaldehyde, OPA or glutaraldehyde. The key is the amount of reagentsuch as sodium bisulfite which is designed to react with the aldehydewithout a color being developed in the presence of an amino acid. Anyremaining aldehyde will then react with the amino acid to develop acolored solution. This confirms the presence of a certain amount of analdehyde such as formaldehyde, OPA or glutaraldehyde in a test solutionsuch as a disinfectant solution. On the other hand, if no color wasdeveloped, it confirms that the formaldehyde, OPA or glutaraldehydeconcentration is below an acceptable specification. The specificconcentration can be set to any point by adjusting the amounts of thechemical reagents used or by using different amounts of aldehyde(formaldehyde, OPA or glutaraldehyde) in the test solution.

Thus, a color pass/fail reaction for determination of excess aldehyde bycontrol of reagents which react with aldehyde is described. The key isthe amount of reagent such as sodium bisulfite which is designed toreact with the Point of Interest (POI) level of aldehyde without a colorbeing developed in the presence of a compound containing an amino groupsuch as an amino acid. Any “extra” aldehyde, exceeding the POI, willthen react with the compound containing an amino group, causing a colorto be developed. In a preferred embodiment, the aldehyde is either OPAor glutaraldehyde and the compound containing the amino group is anamino acid. This method is especially useful for quality control wherecomponents only needed to be examined in pre-determined ranges.

A number of reagents which are known to react quickly with aldehydes maybe used in the practice of the invention. These include any chemicalswhich can oxidize or reduce the aldehyde group and any chemicals whichcan react with and alter the carbonyl functional group of the aldehyde.Examples of such reagents are disclosed in Morrison & Boyd, “OrganicChemistry”, Chapter 19, Allyn and Bacon, 3^(rd) edition, 1973, which isherein incorporated by reference. Such reagents include, but are notlimited to, Ag(NH₃)₂; KMnO₄; K₂Cr₂O₇; H₂+Ni, Pt, or Pd; LiAlH₄ or NaBH₄,then H⁺; Zn (Hg), conc. HCl; NH₂NH₂, base; Grignard reagents; salts ofcyanide and bisulfite; ammonia derivatives such as hydroxylamine,hydrazine, phenylhydrazine, and semicarbazide; reactions with alcoholsin the presence of acid; and reactions with acid or base such as theCannizzaro reaction, the aldol condensation, and the Perkincondensation. In a preferred embodiment, the reagent which reacts withthe aldehyde is a salt of either bisulfite or cyanide.

This aspect of the invention is illustrated in FIG. 1. Both compounds Xand Y react with the aldehyde in the figure. Preferably X reacts muchfaster than Y. Preferably, the reaction of X with aldehyde results in acolorless compound whereas the reaction of Y with aldehyde results in acolored compound. A point of interest is chosen and the amount of X thatwill react with the point of interest is determined. When the aldehydeis mixed with X and Y, the aldehyde will react first with compound Xwhich is kinetically and thermodynamically favored. Any excess aldehydewill then react with compound Y to form a colored solution.Consequently, if a colored solution results, the concentration ofaldehyde is above the point of interest. The determination may be madevisually, with or without a color chart. Alternatively, aspectrophotometer may be used. If the reaction between the aldehyde andcompound X is not kinetically and thermodynamically favored, thencompound Y can be added after the aldehyde reacts with compound X asshown in FIG. 1.

The theoretical amount of OPA: sodium bisulfite is 1:2. However, it wasfound that less sodium bisulfite is needed to react with OPA than thetheoretical amount in order to get a good color display.

Another aspect of the invention is a liquid-measuring device, such as apipette or syringe, for carrying out the assay. This device could beused for any “fixed-volume” measurement and transfer in chemistry,biochemistry, clinical chemistry or other industries.

The apparatus may be a syringe or pipette with one or more barrels andplungers and a membrane barrier with or without a coupling device. Themembrane barrier is a gas or vapor permeable and liquid impermeablebarrier. In the presence of certain pressure differences between the twosides of the barrier, the gas or vapor flows through the membrane butnot the liquid. Any suitable gas or vapor permeable and liquidimpermeable materials can be used for this purpose. Some examplesinclude, but are not limited to, nonwoven polyolefin, such as Tyvek™(non-woven polyethylene), or CSR (non-woven polypropylene central supplyroom), wrapping material and any other hydrophobic filtering materials.Optionally, the device contains an insert and a holder. The syringe orpipette apparatus may also contain valves to control the flow of liquid.

The membrane barrier can be thermally bound to the syringe or pipet. Itcan also be attached to the syringe or pipet with an adhesive orconnected to the syringe barrel by a coupling device. The couplingdevice may be connected to an insert for altering the position of themembrane barrier. The position of the membrane barrier can be adjustedby the length of the insert. The insert may be secured with a holder.

The membrane barrier is a gas or vapor permeable but liquid impermeablebarrier. The membrane barrier is positioned such that the liquid canonly be filled up to the barrier. The invention has several preferredembodiments.

In the first embodiment (FIG. 2), a gas or vapor permeable liquidimpermeable membrane 1 is fixed into the pipette 7 or syringe 6 and heldin place at the desired maximum volume by means known in the art. Thesyringe includes a plunger 3. The syringe can have a metal or plasticneedle with or without a needle cap. In one embodiment (FIGS. 3A–3D), acoupling device 2 is used which is larger or smaller than the diameterof the pipette 7 or syringe 6. Two parts of the pipet or syringe withdifferent lengths can be joined together with such a coupling device.

Coupling of the membrane barrier to the syringe or pipette is shown inFIGS. 3A, 3B, 3C, 3D and FIG. 4. The membrane can be inserted into thesyringe or pipet from the top of the pipette or syringe by an insert 4which may be secured with a holder 5 and its position varied by anymeans known in the art such as by a screw (FIG. 5) or a slidableadjustment (FIG. 4). FIG. 3D shows an insert which has a larger diameterthan the pipette or syringe. By adjusting the insert and creating anegative pressure on the upper part of the pipette or syringe, the fluidcan be loaded into the syringe or pipette up to the barrier.

FIGS. 6A, 6B and 6C illustrate the use of the measuring device with thisinvention. FIGS. 6A and 6B show a syringe with a gas or vapor permeableliquid impermeable barrier and two chemicals. The liquid can be filledin the syringe by inserting the plastic needle into the sample solution,pulling the plunger to create a negative pressure in the syringe, andloading the liquid into the syringe. The measuring device can have afiltering material (FIG. 6A) or valve (FIG. 6B) to retain the chemicalsin the barrel. The chemical in the syringe can be in either a liquid orsolid form. The valve can be a one-way valve or a manual ON/OFF valve.

FIG. 6C provides another embodiment for mixing more than one reactantsuccessively. It has two chambers 9, 10. A fixed volume of any solutionincluding, but not limited to an aldehyde is drawn up through a one-wayvalve or an ON/OFF valve 8 into the first chamber 9 where it mixes withthe first reactant, for example sodium bisulfite. After a predeterminedtime, the reactants flow through a second one-way valve or an ON/OFFvalve 8 into a second reaction chamber 10 which might contain an aminesuch as lysine, for example, to complete the reaction. Alternatively, athree-way valve can be used instead of two one-way valves.

The invention has several advantages over the prior art methods. First,the pass/fail conclusion is consistent and convenient. Preferably, thereis no need to guess the color. The user's only conclusion will be“colored” or “not colored.” Second, the liquid transferring device isconsistent and convenient. A fixed volume of liquid can be taken by asimple operation. Third, the solution color is easier to visualize thana test strip paper since the test strip paper itself is colored, leadingto false positive results. Fourth, the color displaying time can beadjusted by adding a base to make the reaction faster or an acid to makethe reaction slower. Fifth, the color being displayed can be adjusted bychoosing different amino acids or amines. Sixth, the darkness of thecolor being displayed can be adjusted by the amount of the amino acidsor amines. Seventh, the assay is extremely easy to run and interpret.And finally, the liquid transferring device could be used for any“fixed-volume” transfer in chemistry, biochemistry, clinical chemistryor other industries.

EXAMPLES Example 1 Effect of OPA to Sodium Bisulfite Mole Ratio (0.5:1to 8:1)

Sodium bisulfite, glycine and OPA were added in sequence. The OPA tosodium bisulfite mole ratio was adjusted from 0.5:1 to 8:1 (Table 1).Table 1 shows that the solution with a 2:1 ratio developed a color whilea 1:1 ratio did not show color in one week.

It was found that less than the theoretical amount of sodium bisulfitewas needed to react with the OPA. This indicates the OPA solutions inthis concentration region can be differentiated by observing the colorof the solution after a specified time (as in Vial 2 and Vial 3). Sincewe can control the volume of OPA in testing, we can theoretically testan OPA solution in any concentration range.

TABLE 1 Vial 1 Vial 2 Vial 3 Vial 4 Vial 5 NaHSO₃ (82 mM)  200 μl  200μl  200 μl  200 μl  200 μl (0.0164  (0.0164 (0.0164 (0.0164 (0.0164mMole) mMole) mMole) mMole) mMole) Glycine (82 mM) 1600 μL 1600 μL 1600μL 1600 μL 1600 μL (0.1312  (0.1312 (0.1312 (0.1312 (0.1312 mMole) mMolemMole) mMole) mMole) OPA (0.55%, 41 mM)  200 μL  400 μL  800 μL 1600 μL3200 μL (0.00820 (0.0164 (0.0328 (0.0656 (0.1312 mMole) mMole mMole)mMole) mMole) OPA:NaHSO₃ mole 0.5:1 1:1 2:1 4:1 8:1 ratio Time todevelop color >1 week >1 week 4′ 45″ 65″ 35″ Initial color ColorlessColorless Light yel/grn yellow/grn yel/grn Final color (after 30′)Colorless Colorless Dark green Between Dark Blck

Example 2 Effect of OPA to Sodium Bisulfite Mole Ratio (1:1 to 2:1).

Sodium bisulfite, glycine and OPA were added and the OPA to sodiumbisulfite mole ratio was adjusted as in Example 1. Table 2 shows threepoints of interest (POI). The first POI, was the 2:1 mole ratio, thesecond POI was the 1.75:1 mole ratio and the third POI was the 1.5:1mole ratio of OPA to sodium bisulfite. For the 2:1 ratio, 5 minutes wereneeded to display the initial color. For the 1.75:1 ratio, 13 minuteswere needed to display the initial color. For the 1.5:1 ratio, color wasnot displayed for a few days.

TABLE 2 Vial 1 Vial 2 Vial 3 Vial 4 Vial 5 NaHSO₃ (82 mM)  200 μl  200μl  200 μl  200 μl  200 μl (0.0164 (0.0164 (0.0164 (0.0164 (0.0164mMole) mMole) mMole) mMole) mMole) Glycine (82 mM) 1600 μL 1600 μL 1600μL 1600 μL 1600 μL (0.1312 (0.1312 (0.1312 (0.1312 (0.1312 mMole) mMole)mMole) mMole) mMole) OPA (0.55%, 41 mM)  400 μL  500 μL  600 μL  700 μL 800 μL (0.00164 (0.0205 (0.0246 (0.0278 (0.0328 mMole) mMole) mMole)mMole) mMole) OPA:NaHSO₃ mole 1:1 1.25:1 1.5:1 1.75:1 2:1 ratio Time todevelop color Never Never Never 13′ 5′ Initial color Colorless ColorlessColorless Very light (Light) Pink Yel/Grn Final color (after 30′)Colorless Colorless Colorless Green Dark Grn

In Table 2, the reaction volume is varied by varying the amount of OPAsolution from 400 μl to 800 μl. The assay is independent of volume. TheOPA to sodium bisulfite mole ratio is a key parameter of the assay.

Example 3 OPA Concentration Variation Study in the OPA to SodiumBisulfite Mole Ratio 1:1 to 2:1 Region (Same Volume DifferentConcentration)

Sodium bisulfite, glycine and OPA were added and the OPA to sodiumbisulfite mole ratio was adjusted as in Example 2. As shown in Table 3,the first POI was in the range of 6′20″–7′20″ range and the time neededfor color change was very consistent. However, for the second POI, therewas some variation for this time (17–24′). Without being bound by anymechanism, this may be due to the visual limitation or it may mean thatat diluted concentration, the color development is more likely to beinfluenced by micro reaction condition variations, such as temperature,pH or even the exposure of sunlight.

TABLE 3 Vial 1 Vial 2 Vial 3 Vial 4 Vial 5 NaHSO₃ (82 mM)  200 μl  200μl  200 μl  200 μl  200 μl (0.0164 (0.0164 (0.0164 (0.0164 (0.0164mMole) mMole) mMole) mMole) mMole) Glycine (82 mM) 1600 μL 1600 μL 1600μL 1600 μL 1600 μL (0.1312 (0.1312 (0.1312 (0.1312 (0.1312 mMole) mMole)mMole) mMole) mMole) OPA (%)  0.275  0.344  0.413  0.481  0.550 (20.50(25.63 (30.75 (35.88 (41.00 mM mM) mM) mM) mM) ml (0.55% OPA) to diluteto 50.00 62.50 75.00 87.50 No dilution 100 ml with water OPA solutionused  800 μl  800 μl  800 μl  800 μl  800 μl OPA mMole  0.0164  0.0205 0.0246  0.0287  0.0328 OPA:NaHSO₃ mole ratio  1:1  1.25:1  1.5:1 1.75:1  2:1 Time to develop color Never Never Never 17–20′ 6′ 20″–7′20″ Time to develop color, repeat Never Never Never 18–21′ 6′ 20″–7′ 20″#1 Time to develop color, repeat Never Never Never 19–21′ 6′ 20″–7′ 20″#2 Time to develop color, repeat Never Never Never 21–23′ 6′ 20″–7′ 20″#3 Time to develop color, repeat Never Never Never 22–24′ 6′ 20″–7′ 20″#4 Initial color Colorless Colorless Colorless Very (Light) light pinkYel/Grn Final color (after 2 h) Colorless Colorless Colorless Dark GrnDark Grn

Example 4 OPA Concentration Variation Study

Sodium bisulfite, glycine and OPA were added as in Example 1. Since thePOI position is controlled by the OPA to sodium bisulfite mole ratio, bychanging the OPA volume, one should be able to switch the POI tobasically any OPA concentration range. Thus, in Table 4, the actual OPAmoles taken in Vial 1, Vial 2 and Vial 3 are equal to Vial 3, Vial 4 andVial 5 in Table 3.

TABLE 4 Vial 1 Vial 2 Vial 3 NaHSO₃ (82 mM)  200 μl  200 μl  200 μl(0.0164 mMole) (0.0164 mMole) (0.0164 mMole) Glycine (82 mM) 1600 μL1600 μL 1600 μL (0.1312 mMole) (0.1312 mMole) (0.1312 mMole) OPA (%, 41mM)  0.275  0.344  0.413 ml (0.55% OPA) to dilute to 50.00 62.50 75.00100 ml OPA solution used 1201 μl 1119 μl 1065 μl (0.0246 mMole) (0.0287mMole) (0.0328 mMole) OPA:NaHSO₃ mole ratio  1.5:1  1.75:1  2:1 Time todevelop color (up to Never 16′  5′ 30′) Initial color Colorless (light)Yel/Grn (Light) Yel/Grn

Thus, one of the key factors for this invention is the mole ratio ofaldehyde to sodium bisulfite. Similar results were obtained forDL-alanine, ε-amino-n-caproic acid and L-lysine, except that differentend colors were observed.

Example 5 Further Experiments with OPA for POI's in the Range of 0.35%and 0.30%

Changes due to the type of amino acid and the mole ratio wereillustrated in the following example where DL-dopa is used as the aminoacid (also see Example 7). Sodium bisulfite, and OPA were added as inExample 1. DL-dopa was substituted for glycine as the amino acid.

TABLE 5 82 mM NaHSO3 Saturated 0.35% OPA 0.30% OPA 0.35% OPA 0.30% OPADL-dopa (23.09 mM) (22.37 mM) (23.09 mM) (22.37 mM) Color in Color in(minutes and (minutes and seconds) seconds) 100 μl 100 μl 450 μl 450 μl2′20″–2′30″ 3′20″–4′ (0.0082 mMole) (0.0119 (0.0101 mMole) mMole) 100 μl100 μl 400 μl 400 μl 3′00″–3′30″ 5′–10′ (0.0082 mMole) (0.0106 (0.0089mMole) mMole) 100 μl 100 μl 390 μl 390 μl 3′40″–4′10″ 5′30″–11′ (0.0082mMole) (0.0103 (0.0087 mMole mMole

In the above example, the use of DL-dopa as the amine resulted in anorange color. The type of amino acid, mole ratio, and reaction time areall important to determine the formation of color.

Example 6 Base Effect for the Color Development Time

This example shows that added base promotes the reaction rate so thatthe color displaying time can be shortened. Thus, a certain amount ofbase could be added to display the color within a desired period oftime.

TABLE 6 Vial 1 Vial 2 Vial 3 Vial 4 NaHSO₃ (82 mM)  200 μl  200 μl  200μl  200 μl (0.0164 (0.0164 (0.0164 (0.0164 mMole) mMole) mMole) mMole)Glycine (82 mM) 1600 μL 1600 μL 1600 μL 1600 μL (0.1312 (0.1312 (0.1312(0.1312 mMole) mMole) mMole) mMole) OPA (%) (variation conc.)  0.275 0.344  0.413  0.481 ml (0.55% OPA), added to dilute to 50.00 62.5075.00 87.50 100 ml OPA (0.55%, 41 mM)(initial conc.)  800 μl  800 μl 800 μl  800 μl (0.0164 (0.0205 (0.0246 (0.0287 mMole) mMole) mMole)mMole) OPA:NaHSO₃ mole ratio  1:1  1.25:1  1.5:1  1.75:1 Time to developcolor (without colorless colorless colorless Very light NaOH) pink(17′–24′) Time to develop color (100 μL 1.5 h slight 1 h slight 2′yellow <2′, yellow NaOH added) yellow yellow Time to develop color (200μL All turned yellow in less than 1′. Too fast. Too much NaOH added)base. Note: Sodium hydroxide was added before OPA.

Conversely, it was found that added acid, such as citric acid, woulddelay the color display. This would be useful in the case if the coloris displayed too soon (data not shown).

Example 7 Other Amino Acids with Added Base (100 μL)

It was found with other amino acids that the displayed colors weredifferent. For example, when reacting with OPA, DL-alanine was brightyellow and for ε-amino-n-caproic acid, the color was pink. Furthermore,the reaction rates were also different. Thus both DL-alanine andε-amino-n-caproic acid displayed color significantly later than glycine(data not shown).

Example 8 Activated Cidex Solution (Containing 2.1% Glutaraldehyde) withLysine

To five scintillation vials, glutaraldehyde, sodium bisulfite and lysinewere added and mixed. A yellow color developed gradually from Vial 5. Nocolor was observed in Vial 1. The “between” colors were seen from Vial 2to Vial 4 but they are so “gradual” that they could not be distinguishedvisually.

TABLE 7 Vial 1 Vial 2 Vial 3 Vial 4 Vial 5 NaHSO₃ (82 mM)   200 μl   200μl   200 μl   200 μl   200 μl (0.0164 (0.0164 (0.0164 (0.0164 (0.0164mMole) mMole) mMole) mMole) mMole) Lysine (82 mM)  1600 μl  1600 μl 1600 μl  1600 μl  1600 μl (0.1312 (0.1312 (0.1312 (0.1312 (0.1312mMole) mMole) mMole) mMole) mMole) Glutaraldeyde (220 mM) solution used 74.5 μl  93.2 μl 111.8 μl 130.5 μl 149.1 μl (0.0614 (0.0205 (0.0246(0.0287 (0.0328 mMole) mMole) mMole) mMole) mMole) Glutaraldehyde:NaHSO₃mole ratio 1:1 1.25:1 1.5:1 1.75:1 2:1 Color at 15 minutes ColorlessVery light yellow to yellow, very Yellow gradual. No clear-cutdifference

This can be explained in light of the stabilities of the compoundsinvolved. First, if aldehyde-sodium bisulfite complex 5 is more stablethan aldehyde-sodium bisulfite complex 6, we would see a larger POIrange from glutaraldehyde.

Or in more accurate terms, the different POI ranges from OPA andglutaraldehyde might be a result of the competence of aldehyde-sodiumbisulfite formation and the aldehyde/amino acid Schiff's base formationboth kinetically and thermodynamically.

In Route 1, when the three components are mixed together, the formationof compound 5 is more favorable than the formation of compound 7, bothkinetically and thermodynamically.

This is somewhat different in the situation of Route 2. Although theformation of 6 is still more favorable than that of 9, the difference ismuch smaller than that between 7 and 5 in Route 1. Therefore if thethree components (glutaraldehyde, sodium bisulfite and lysine) aremixed, depending on the ratio, there may be some small amount of 9formed which results in a detectable yellow color. However, thissituation is manipulated by mixing of compound 8 and NaHSO₃ first andadding lysine last. In this case, if there is no aldehyde left, lysinemust compete with 6 to form 9, which is not very favorable. With somecombinations of amino acid and aldehyde, the order of adding thereactants may be important. In the following example, the amino acid wasadded last.

Example 9 Amino Acid was Added Last

To five scintillation vials, glutaraldehyde and sodium bisulfite wereadded and mixed first, and lysine solution was added last respectively.A yellow color developed gradually from Vial 5 to Vial 2 but not in Vial1 (Table 8).

TABLE 8 Vial 1 Vial 2 Vial 3 Vial 4 Vial 5 NaHSO₃ (82 mM)   200 μl   200μl   200 μl   200 μl   200 μl (0.0164 (0.0164 (0.0164 (0.0164 (0.0164mMole) mMole) mMole) mMole) mMole) Lysine (82 mM)  1600 μL  1600 μL 1600 μL  1600 μL  1600 μL (0.1312 (0.1312 (0.1312 (0.1312 (0.1312mMole) mMole) mMole) mMole) mMole) Glutaraldehyde (220 mM) solution 74.5 μl  93.2 μl 111.8 μl 130.5 μl 149.1 μl used (0.0614 (0.0205(0.0246 (0.0287 (0.0328 mMole) mMole) mMole) mMole) mMole)Glutaraldehyde: NaHSO₃ mole 1:1 1.25:1 1.5:1 1.75:1 2:1 ratio Color at15′ Colorless light yellow yellow yellow yellow

A narrower POI range was observed for glutaraldehyde reacting withlysine and sodium bicarbonate. Adding the amino acid (lysine) last wasthe key. Table 8 shows a clear color difference between Vial 1 (colorless) and Vial 3 (yellow). Thus by allowing the glutaraldehyde andsodium bisulfite to react first and then adding lysine, results aresimilar to those observed with OPA above.

Depending on the chemicals used, the time may vary. For NaHSO₃, thelysine can be added immediately after the aldehyde is mixed with theNaHSO₃. Thus the assay described can be applied generally to aldehydesand amines to provide a pass/fail type assay of aldehyde content.

Example 10

The above chemistry principle may be applied in the reaction ofaldehydes and compounds containing an amino group generally. Thisexample shows the reaction of glutaraldehyde and sodium cyanide usingeither glycine or lysine as the amino acid. The formation ofcorresponding two aldehyde cyanide addition compounds are shown asbelow.

The Formation of Colorless Aldehyde-Cyanide Addition Compounds 10 and 11

To each of the 5 scintillation vials, glutaraldehyde and sodium cyanidewere added and mixed first (Table 9), and lysine solution was addedlast. A yellow color developed from Vial 5 but not from the other vials.A POI was identified between Vial 4 and Vial 5.

TABLE 9 Glutaraldehyde:Sodium Cyanide Mole Ratio (0.125:1 to 2:1). Vial1 Vial 2 Vial 3 Vial 4 Vial 5 NaCN (82 mM)   200 μl   200 μl   200 μl  200 μl   200 μl (0.0164 (0.0164 (0.0164 (0.0164 (0.0164 mMole) mMole)mMole) mMole) mMole) Glycine (82 mM)  1600 μL  1600 μL  1600 μL  1600 μL 1600 μL (0.1312 (0.1312 (0.1312 (0.1312 (0.1312 mMole) mMole) mMole)mMole) mMole) Glutaraldehyde (220 mM) solution  9.3 μl  18.6 μl  37.3 μl 74.5 μl 149.1 μl used (0.0020 (0.0041 (0.0082 (0.0164 (0.0328 mMole)mMole) mMole) mMole) mMole) Glutaraldehyde:NaCN mole ratio 0.125:10.25:1 0.5:1 1:1 2:1 Final color in 7′ Colorless Colorless ColorlessColorless Yellow

Example 11

To each of the 5 scintillation vials, glutaraldehyde and sodium cyanidewere added and mixed first, and lysine solution was added last (Table10). A yellow color developed from Vial 2 to Vial 5 but not recognizablefrom Vial 1. A POI was identified between Vial 1 and Vial 3. It is onlypractical with the naked eye to differentiate the colors between Vial 1and Vial 3. That is, it would be challenging to distinguish thedifference between Vial 1 and Vial 2 or between Vial 2 and Vial 3. Thuswe may conclude that no narrower POI could be identified unless aninstrument is employed.

TABLE 10 Glutaraldehyde:Sodium Cyanide Mole Ratio (1:1 to 2:1). Vial 1Vial 2 Vial 3 Vial 4 Vial 5 NaCN (82 mM)   200 μl   200 μl   200 μl  200 μl   200 μl (0.0164 (0.0164 (0.0164 (0.0164 (0.0164 mMole) mMole)mMole) mMole) mMole) Glycine (82 mM)  1600 μL  1600 μL  1600 μL  1600 μL 1600 μL (0.1312 (0.1312 (0.1312 (0.1312 (0.1312 mMole) mMole) mMole)mMole) mMole) Glutaraldehyde  74.5 μl  93.2 μl 111.8 μl 130.5 μl 149.1μl (220 mM) solution (0.0164 (0.0205 (0.0082 (0.0164 (0.0328 used mMole)mMole) mMole) mMole) mMole) Glutaraldehyde:NaCN 1:1 1.25:1 1.5:1 1.75:12:1 mole ratio Time to develop color Never 3′ 2′ 1′ 1′ Color in ~8minutes Colorless Very light Yellow Yellow Yellow Yellow

The aldehyde solution can be measured and transferred by means known inthe art such as by a regular pipet or syringe. In a preferredembodiment, the aldehyde solution can be measured and transferred usinga liquid measuring device as described herein which features a gas orvapor permeable, liquid impermeable, membrane. The use of the liquidmeasuring device containing the gas or vapor permeable, liquidimpermeable membrane of the present disclosure has the advantage thatthe liquid can be transferred easily using a simple operation withconsistent results.

Compound X and Compound Y (FIG. 1) may be in one vial or in two separatevials. They may be transferred using either a pipet or syringe. Thealdehyde may be added to compound X and the resulting mixture added tocompound Y, the aldehyde may be added to compounds X and Y together, orthe aldehyde and chemical Y can be added to the chemical Xconsecutively. The measuring and/or transferring of the aldehyde testsample can be conducted with a regular pipet or syringe. The gas orvapor permeable liquid impermeable barrier adds many benefits asdescribed previously.

In one embodiment, shown in FIG. 6C, the Compound X may be in a firstchamber 9. The aldehyde is drawn up through the valve 8 up to the gas orvapor permeable, liquid impermeable barrier 1. After a predeterminedtime, the aldehyde and compound X are transferred to a second chamber 10through a valve 8 which is either a one-way or an on/off valve, wherethey react with compound Y. After a pre-determined time, the color inthe second chamber is observed and the presence or absence of excessaldehyde in the test sample is determined.

It will be understood by those of skill in the art that numerous andvarious modifications can be made without departing from the spirit ofthe present invention. Therefore, it should be clearly understood thatthe forms of the present invention are illustrative only and are notintended to limit the scope of the present invention.

1. A liquid measuring device that measures a fixed volume of liquidcomprising: a first barrel having a proximal and distal end; a couplingdevice comprising a gas or vapor permeable but liquid impermeablebarrier on a second barrel, said second barrel being movable along thefirst barrel to adapt the barrier to the measuring device, whereby thefixed volume of liquid is adjusted by moving said coupling device alongthe first barrel; a gas, vapor and liquid impermeable element adapted tothe measuring device to provide a pressure difference between two sidesof the barrier such that the liquid can only be filled from the distalend of the first barrel up to the barrier; a valve and a needle at thedistal end.
 2. The liquid measuring device of claim 1, wherein thevolume in the first barrel up to the barrier equals said fixed volume.3. The liquid measuring device of claim 1, further comprising a holderto position and secure said coupling device in the liquid measuringdevice.
 4. The liquid measuring device of claim 3, wherein the couplingdevice is moved to a desired position by means of a screw.
 5. The liquidmeasuring device of claim 3, wherein the coupling device is moved to adesired position by pushing or pulling the second barrel along the firstbarrel.
 6. The liquid measuring device of claim 1 which is a syringe. 7.The liquid measuring device of claim 1, which further comprises a thirdbarrel which is in fluid communication with said first barrel by meansof a valve.
 8. The liquid measuring device of claim 1, wherein said gasor vapor permeable but liquid impermeable barrier comprises hydrophobicmaterial.